Brazilian Jiu-Jitsu emphasizes getting an opponent to the ground to be able to utilize ground fighting methods and submission holds involving joint-locks and chokeholds. The premise is that most of the benefit of a larger, stronger opponent comes from superior reach and more powerful strikes, jiu jitsu training both of which are notably negated when grappling on the ground.
BJJ permits numerous techniques to simply take the fight to the ground after taking a grip. Once the opponent is on the ground, a number of maneuvers (and counter-maneuvers) can be found to manipulate the opponent into a suitable position for the application of a submission technique. Achieving a dominant position on the ground is one of the hallmarks of the ju jitsu, and includes effective use of the guard position to defend oneself from bottom, and passing the guard to dominate from top position with side control, mount, and back mount positions. This technique of maneuvering and manipulation could be likened to a kind of kinetic chess when utilized by two experienced practitioners. A submission hold is the equivalent of checkmate in the sport, reflecting a disadvantage which would be exceptionally difficult to overcome in a fight (such as a dislocated joint or unconsciousness).